Processes can now eat from writeable addresses only.

I've found that allowing organisms to eat from everywhere (including
addresses owned by other organisms) made the simulation too unstable.
Organisms may now eat from either free memory, or from self-owned
memory.

1 files changed, 9 insertions, 2 deletions

diff --git a/src/process.c b/src/process.c
index 8d500ae..4004ae1 100644
--- a/src/process.c
+++ b/src/process.c
@@ -1286,7 +1286,13 @@ static boolean eat_seek(uint32 pidx, boolean forward)
 		return FALSE;
 	}
 
-	if (g_procs[pidx].sp == next_addr) {
+	/* Processes may only eat code copies from memory areas that are either
+	deallocated or owned by them (i.e. writeable).
+	*/
+	if (
+		!is_writeable_by(pidx, g_procs[pidx].sp) ||
+		g_procs[pidx].sp == next_addr
+	) {
 		increment_sp(pidx, forward);
 		return FALSE;
 	}
@@ -1313,7 +1319,8 @@ static void eat(uint32 pidx)
 
 	However, whenever an organism eats, the detected copy of the source code
 	gets destroyed (randomized). The main idea of the EAT instruction is to
-	turn 'information' into a valuable resource in Salis.
+	turn 'information' into a valuable resource in Salis. Organisms,
+	nonetheless, may only eat information which they have 'write' access to.
 	*/
 	uint32 source;
 	uint32 target;